This invention relates in general to bearings and more particularly to a clamp-up device for properly positioning such bearings on shafts such as the necks of mill rolls.
The bearings used in rolling mill stands must not only be capable of supporting the mill rolls, but must also resist the tremendous forces applied to such rolls with sufficient rigidity to enable metal shapes to be rolled to within close tolerances. Where high rolling speeds are employed, it is desirable to have the inner race of each bearing fitted tightly to its roll neck to eliminate neck scuffing and wear. Similarly, tight fits improve the stability of the roll mounting and are frequently required where the rolling must be performed with considerable percision.
While any bearing can be tightly fitted to a shaft or roll neck, merely by creating an interference fit, the better procedure is to taper the roll neck at each of the roll ends and use on that roll neck a bearing having the bore of its inner race, or cone bore in the case of a tapered roller bearing, tapered to conform to the taper of the roll neck. These bearings, in comparison with loosely fitted bearings, are somewhat more difficult to install on and to withdraw from their tapered roll necks because of the tight fits that are involved. Indeed, various hydraulic appliances are required for both installation and removal.
With regard to installation, the bearing is manipulated over the roll neck until the cone fits loosely on the tapered portion of the neck. Then a hydraulic ring jack is placed over the roll neck adjacent to the outer end of the bearing, and a split hinged ring is fitted into a groove within the roll neck to serve as a backing for the ring jack. Once the ring jack is in place, lines from a hydraulic pump are connected to it and it is pressurized so that it expands axially and forces the inner race of the bearing up the taper of the roll neck until the inner race is tightly seated. The jack is then removed and replaced with a clamping nut and a ring over which the nut threads. This requires removal of the split hinged ring followed by removal of the jack. The nut and threaded ring, in a contracted condition, are then passed over the roll neck to the place formerly occupied by the jack, and the split hinged ring is replaced. Finally the nut is tightened, usually with a spanner wrench, to hold the bearing fast.
To remove the bearing, the nut must be loosened, and usually this requires a special hydraulic wrench which is installed over the roll neck and nut, since after a short period of mill operation the nut is usually so tight that it cannot be loosened with a manually manipulated wrench. Once the split hinged ring and nut are removed, the inner race is usually expanded slightly by forcing pressurized hydraulic fluid through drilled holes and into annular grooves, the latter of which open out of the roll neck and toward the surface of the tapered cone bore. This breaks the grip of the cone on the tapered roll neck.
Both the installation and removal of a tightly fitted roll neck bearing from a tapered roll neck are burdensome and time consuming procedures. Inasmuch as the rolls of rolling mills receive a considerable amount of abuse, they must be replaced often. Under these circumstances, it is desirable to make the replacement as easy and as quick as possible.